Conic micro-electro-mechanical system (MEMS) micro-mirror array (MMA) steered active situational awareness sensor

Abstract

An active situational sensor uses a beam steerer to steer a spot-beam onto a conical shape of a fixed mirror oriented along an optical axis to scan a FOR. The sensor may rapidly scan a 360° horizontal FOR with a specified vertical FOR or any portion thereof, move discretely between multiple specific objects per frame, vary the dwell time on an object or compensate for other external factors to tailor the scan to a particular application or changing conditions in real-time. The fixed mirror includes a MEMS MMA that approximates the conical shape of the mirror. The MEMS MMA being configurable to extend the vertical FOR or shape the spot-beam to adjust size, focus or intensity profile or to produce deviations in the wavefront of the spot-beam to compensate for path length differences or atmospheric distortion. The MEMS MMA being configurable to produce and independently steer a plurality of spot-beams of the same or different wavelengths.

We claim: 
     
       1. A situational awareness sensor, comprising:
 a laser configured to generate a beam of optical radiation; 
 a fixed mirror having a conical shape oriented along an optical axis; 
 a beam steerer responsive to command signals to focus the optical radiation into a spot-beam on the conical shape of the fixed mirror and steer the spot-beam in two-dimensions about the optical axis to re-direct the spot-beam to scan a field-of-regard (FOR) in a first angular direction around the optical axis; 
 said fixed mirror comprising a Micro-Electro-Mechanical System (MEMS) Micro-Mirror Array (MMA) including a plurality of mirrors that in combination approximate the conical shape, said mirrors responsive to command signals to tip and tilt to scan the spot-beam in a second angular direction along the optical axis to expand the FOR in the second angular direction; and 
 a detector configured to sense a reflected component of the spot-beam, 
 wherein the beam steerer responsive to command signals steers the spot-beam axially along the conic shape of the fixed mirror to scan the FOR in the second angular direction, said FOR in the second angular direction being expanded by operation of the MEMS MMA. 
 
     
     
       2. The situational awareness sensor of  claim 1 , wherein the beam steerer comprises one of a gimbaled mirror, a liquid crystal waveguide (LCWG) or a steering MEMS MMA. 
     
     
       3. The situational awareness sensor of  claim 1 , wherein the beam steerer comprises an N-port optical switch configured to selectively route the beam from 1 of N ports at discrete steering angles about the optical axis spaced around the conical shape of the fixed mirror and focus the optical radiation into the spot-beam on the conical shape of the fixed mirror to re-direct the spot-beam to scan a field-of-regard (FOR) at discrete scan angles in a first angular direction around the optical axis, said MEMS MMA's mirrors responsive to command signals to tip and tilt to scan the spot-beam in the first angular direction to span the discrete scan angles and provide a continuous FOR in the first angular direction. 
     
     
       4. The situational awareness sensor of  claim 1 , wherein the fixed mirror comprises at least three triangular-shaped planar MEMS MMAs configured to form an N-sided pyramid that approximates the conic shape of the fixed mirror. 
     
     
       5. The situational awareness sensor of  claim 1 , wherein the fixed mirror comprises one or more MEMS MMAs formed on a flexible substrate and wrapped on a conic mandrel to approximate the conic shape of the fixed mirror. 
     
     
       6. A situational awareness sensor, comprising:
 a laser configured to generate a beam of optical radiation; 
 a fixed mirror having a conical shape oriented along an optical axis; 
 a beam steerer responsive to command signals to focus the optical radiation into a spot-beam on the conical shape of the fixed mirror and steer the spot-beam in two-dimensions about the optical axis to re-direct the spot-beam to scan a field-of-regard (FOR) in a first angular direction around the optical axis; 
 said fixed mirror comprising a Micro-Electro-Mechanical System (MEMS) Micro-Mirror Array (MMA) including a plurality of mirrors that in combination approximate the conical shape, said mirrors responsive to command signals to tip and tilt to scan the spot-beam in a second angular direction along the optical axis to expand the FOR in the second angular direction; and 
 a detector configured to sense a reflected component of the spot-beam, 
 wherein the beam steerer comprises: 
 a parabolic mirror having a hole formed at its center through which the beam of optical radiation passes; and 
 a steering MEMS MMA positioned in front of the parabolic mirror to receive the beam, said steering MEMS MMA comprising one or more independent and continuously controlled mirrors that tip and tilt to steer the beam onto different off-axis sections of the parabolic mirror that focus the optical radiation into the spot-beam and steer the spot-beam about the optical axis. 
 
     
     
       7. The situational awareness sensor of  claim 6 , wherein the mirrors of the fixed mirror's MEMS MMA and the steering MEMSM MMA are further configured to piston to shape the spot-beam. 
     
     
       8. A situational awareness sensor, comprising:
 a laser configured to generate a beam of optical radiation: 
 a fixed mirror having a conical shape oriented along an optical axis; 
 a beam steerer responsive to command signals to focus the optical radiation into a spot-beam on the conical shape of the fixed mirror and steer the spot-beam in two-dimensions about the optical axis to re-direct the spot-beam to scan a field-of-regard (FOR) in a first angular direction around the optical axis, 
 said fixed mirror comprising a Micro-Electro-Mechanical System (MEMS) Micro-Mirror Array (MMA) including a plurality of mirrors that in combination approximate the conical shape, said mirrors responsive to command signals to tip and tilt to scan the spot-beam in a second angular direction along the optical axis to expand the FOR in the second angular direction; and 
 a detector configured to sense a reflected component of the spot-beam, wherein the beam steerer comprises: 
 a steering MEMS MMA positioned to receive the beam at an angle of incidence, said steering MEMS MMA comprising a plurality of independent and continuously controlled mirrors that approximate an off-axis section of a parabolic surface to re-direct and focus the optical radiation into the spot-beam on the conical shape of the fixed mirror, said mirrors responsive to command signals to tip, tilt and piston each mirror to steer the spot-beam in two-dimensions about the optical axis. 
 
     
     
       9. The situational awareness sensor of  claim 8 , wherein the mirrors of the fixed mirror's MEMS MMA and the steering MEMS MMA are further configured to piston to shape the spot-beam. 
     
     
       10. A situational awareness sensor, comprising:
 a laser configured to generate a beam of optical radiation; 
 a fixed mirror having a conical shape oriented along an optical axis; 
 a beam steerer responsive to command signals to focus the optical radiation into a spot-beam on the conical shape of the fixed mirror and steer the spot-beam in two-dimensions about the optical axis to re-direct the spot-beam to scan a field-of-regard (FOR) in a first angular direction around the optical axis; 
 said fixed mirror comprising a Micro-Electro-Mechanical System (MEMS) Micro-Mirror Array (MMA) including a plurality of mirrors that in combination approximate the conical shape, said mirrors responsive to command signals to tip, tilt and piston to scan and shape the spot-beam in a second angular direction along the optical axis to expand and scan the FOR in the second angular direction; and 
 a detector configured to sense a reflected component of the spot-beam. 
 
     
     
       11. The situational awareness sensor of  claim 10 , wherein each said mirror rotates about X and Y orthogonal axes, respectively, and translates along a Z axis orthogonal to the XY plane to tip, tilt and piston, respectively. 
     
     
       12. The situational awareness sensor of  claim 11 , wherein each said mirror is supported at three vertices of a triangle, wherein lines defined by three different pairs of said vertices provide three axes at 60 degrees to one another in the XY plane, wherein each said mirror pivots about each said axes to produce tilt, tip and piston in an XYZ space. 
     
     
       13. The situational awareness sensor of  claim 10 , wherein the mirrors are configured to at least partially collimate the spot-beam. 
     
     
       14. The situational awareness sensor of  claim 10 , wherein said mirrors tip, tilt and piston to shape the spot-beam to perform one or more of the following:
 adjust a size, divergence or intensity profile of the spot-beam; 
 produce deviations in the wavefront of the spot-beam to compensate for atmospheric distortion; and 
 adjust the phase and maintain a zero phase difference across the spot-beam. 
 
     
     
       15. A situational awareness sensor, comprising:
 a laser configured to generate a beam of optical radiation; 
 a fixed mirror having a conical shape oriented along an optical axis; 
 a beam steerer responsive to command signals to focus the optical radiation into a spot-beam on the conical shape of the fixed mirror and steer the spot-beam in two-dimensions about the optical axis to re-direct the spot-beam to scan a field-of-regard (FOR) in a first angular direction around the optical axis; 
 said fixed mirror comprising a Micro-Electro-Mechanical System (MEMS) Micro-Mirror Array (MMA) including a plurality of mirrors that in combination approximate the conical shape, said mirrors responsive to command signals to tip and tilt to scan the spot-beam in a second angular direction along the optical axis to expand the FOR in the second angular direction; and 
 a detector configured to sense a reflected component of the spot-beam, 
 wherein the MEMS MMA is partitioned into a plurality of segments illuminated by the spot-beam, each segment including at least one mirror, said MEMS MMA responsive to tip and tilt the mirrors in each segment to separate the spot-beam into a plurality of spot-beams to scan the FOR. 
 
     
     
       16. The situational awareness sensor of  claim 15 , wherein the MEMS MMA is partitioned into a plurality of segments illuminated by the spot-beam, each segment including at least one mirror, said MEMS MMA responsive to tip, tilt and piston the mirrors in each segment to separate the spot-beam into a plurality of spot-beams to scan the FOR. 
     
     
       17. A situational awareness sensor, comprising:
 a laser configured to generate a beam of optical radiation; 
 a fixed mirror having a conical shape oriented along an optical axis; 
 a beam steerer responsive to command signals to focus the optical radiation into a spot-beam on the conical shape of the fixed mirror and steer the spot-beam in two-dimensions about the optical axis to re-direct the spot-beam to scan a field-of-regard (FOR) in a first angular direction around the optical axis; 
 said fixed mirror comprising a Micro-Electro-Mechanical System (MEMS) Micro-Mirror Array (MMA) including a plurality of mirrors that in combination approximate the conical shape, said mirrors responsive to command signals to tip and tilt scan the spot-beam in a second angular direction along the optical axis to expand the FOR in the second angular direction and to tip, tilt and piston to shape and at least partially collimate the spot-beam that scans the FOR; and 
 a detector configured to sense a reflected component of the spot-beam.